It's hard to say for certain. Cats have a strong sense of smell and may use scent to recognize their kittens, especially when young. Vocalizations and familiarity may also play a role, but every cat is different.
Research suggests limited recognition after long separations, and the mother-kitten bond may weaken as kittens become independent. Scent, vocalizations, and familiarity likely all contribute to any recognition that occurs.